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I'm using a shooting board to get good edges on a back set prior to joining them. One set was done very easily, but now I'm working on a set where I seem to be chasing my tail. The gap seems to move around. At the moment I have a gap in the middle and both ends are tight. I decided to step away from it for a day. This back set is a bit more cupped/uneven -- not quite a potato chip -- but it needs to be held flat.

What are your techniques to deal with a back set that won't shoot straight?

put a pic of you board. Sometimes it is the wood.
I use a granite plate to sand the joint true.

I use a granite plate to sand the joint true

As luck would have it I just got a granite plate. I was wondering what I could use it for.

Dumb question, but are you sanding one direction or back and forth? Back and forth will produce the problems you mentioned. Then, if you take the set off of the shooting board to check to see if they're closed, then put them on upside-down, or shoot them back and forth the opposite direction, you'll get the opposite problem, ie if you had a rounded center, you'll now have a gap. I did this with my first few tops and chased my tail, sometimes for a couple of days. It was very frustrating. Then it dawned on me that I had to sand or plane from 1 direction only, and make sure that after checking my progress that I return the set to the shooting board exactly the same orientation. Now I take about 15 minutes on average to shoot a set.

This is my shooting board. It consists of 2 boards, each 3/4" thick, the bottom ~2" wider than the top, where a straight edge or plane can ride along the edge of the top board. This photo shows a top in it.

The wood strip to the left, is a back stop. Down the center is a 2" wide x 3/4" thick strip of wood with wing nuts on each end to hold the set that I'm shooting tight to the board. It takes care of cupping and keeps the set absolutely tight to the board while I shoot.

I am going to add another strip of wood closer to the shooting edge. On rare occasion there can still be a little bit of cupping on really squirrely wood. It's rare that the bar down the center doesn't take care of it, but it happens.

I have to say that after jointing 1000s of tops I learned a thing or 2
You can sand very true but you have to be ergonomic in the endeavor. If you have issues make a squareing fence to help hold things flat
I don't use my arms I use my legs and don't use a lot of pressure. The harder you push the more you stress the joint . You tube the subject you will find lots of info

Planing technique has a lot to do with it. We tend to think of a hand plane as a hand powered electric jointer where it is not. The jointer has 2 parallel tables that are offset the amount of the cut, where the hand plane is one long flat surface with the blade sticking down in the middle of it, so think a bit about that relationship. How can it possibly produce a flat surface? The way you start and the way you end is critical, and there is a lot of advice on that on YT. It takes practice to get it to work right - and oh, yea - plane from the same direction each time like they said.

Think about this - a completely flat plane sole was never an issue til us Yuppie Bastards came on the scene. The craftsman who relied on them just learned how to do what they wanted to do with the plane they had. I have a Number 7 (22" jointer plane) that is exceptionally out of flat and I got it from a very old guy who was a consummate woodworker.

Ed

I have some very nice planes for jointing tops and backs, which include a 22" and a 24" Bailey, and my go to plane which is a Lie-Nielsen 14" low angle Jack plane. Some years ago a now deceased but very famous Flamenco and Classical guitar maker came to Hawaii and ended up staying at my house/shop for a few days. We did some work together, and when it came to joining a top he asked for a sharp block plane. I thought it was a strange choice, but he did a great job of jointing a top. It's so much about just learning to use what you've got.--Bob

Sorry for the double post! Can't figure out how to delete it.--Bob

Great topic, thanks for asking about this. I just attempted my first back joint, and it was a bit puzzling. Ran them over the jointer first - close, but not perfect. Then to the shooting board, my first experience with this legend. Learned early on that things needed to be clamped and the strokes needed to be deliberate - I knew not to rock the plane (Bailey #5) but it took some practice to avoid it, was trying to keep the pressure in one spot. I got lucky - after one particular set of passes, for no particular reason they just clonked together, but then I blew the glue up so I get some more practice! But the process illustrated that this could be a real tail chaser - how do you make these micro adjustments with a 14" plane? The granite plate idea is very interesting - need to look this up on YT